M.S., Moscow Institute of Physics and Technology (2001) Ph.D., University of Pittsburgh (2005) Postdoctoral Research Associate, Lawrence Berkeley National Laboratory, (2005-2007)

Analytical Chemistry/Physical Chemistry

Our research focuses on a single molecule level study of the mechanical, optical and conductive properties of molecular junctions composed a few molecules up to molecular films that will enable the design and fabrication of molecular devices with useful electrical, mechanical and optical properties. We are also interested in the chemical speciation and environmental processing of individual submicron atmospheric aerosols and their impact on the climate and environment. Opto-Electromechanical Properties of Nanostructured Materials Molecular devices offer not only an ultra-miniaturization of electric devices but can also exhibit novel and significantly improved physical, chemical, and optical properties and phenomena that are unique to this size scale and may not be as predictable as those observed at larger scales. Presently, molecular devices fail frequently and are difficult to control and replicate, in part due to the severe geometric constraints under which they are constructed and connected to external circuitry. The feasibility of these devices depends on our ability to understand and control specific properties of individual or bundles of molecules and to connect these nanostructures to the macroscopic world. The goal of this research program is quantitative physical chemistry studies to correlate conducting, optical, structural and mechanical properties of molecular nanojunctions with potential use in opto-electromechanical molecular devices. These include studies of molecule-electrode contact effects under the influence of applied force and elucidation of the charge transfer mechanisms of cooperative effects between interacting molecules forming nanojunctions, with the aim of developing mechanically stable, reliable and efficient electrical contacts and interconnects. Conductive probe atomic force microscopy and scanning force spectroscopy techniques are employed to repeatedly form metal-molecule(s)-metal junctions and study their properties. We are examining the properties of these junctions under different temperatures as a function of molecular length, molecule-electrode contact type, number of molecules forming the nanojunction, AFM probe material, mechanically induced stress and strain, and under different organic solvents and inert gases. Chemical Speciation and Environmental Processing of Atmospheric Aerosols Atmospheric aerosols have substantial effects on the atmospheric radiative budget either by directly scattering and absorbing solar radiation or indirectly by acting as cloud condensation nuclei and facilitating the formation of aqueous aerosol. These direct and indirect effects lead to a warming and cooling of the atmosphere, respectively. The overall climate effect of increasing atmospheric aerosol concentrations remains largely unknown, primarily due to large uncertainties in the chemical composition of aerosols as well as a limited understanding of the chemical transformations and atmospheric lifetimes of particles due to atmospheric processing. We are developing a novel approach for reactive spectromicroscopy studies of single aerosols based on a combination of scanning transmission x-ray microscopy and near edge x-ray absorption fine structure spectroscopy. This combination provides a unique opportunity to identify functional groups within various regions of individual submicron particles. One of the goals of our research is in situ chemical kinetics study of both the chemical and morphological changes of individual atmospheric particles during chemical transformations. Chemical transformations include oxidation of these particles with atmospheric trace gases (e.g. NO2, SO2, H2SO4, NHO3) followed by water uptake. These studies are important to understand the chemical composition and environmental processing of atmospheric aerosols and hence radiative forcing.

Moffet, R. C.; Tivanski, A. V.; Gilles, M. K. "Scanning Transmission X-ray Microscopy: Applications in Atmospheric Aerosol Research, in Fundamentals and Applications of Aerosol Spectroscopy," eds Ruth Signorell and Jonathan P. Reid ,Taylor and Francis Books, Inc. in press, 2010. Moffet, R. C.; Henn, T. R.; Tivanski, A. V.; Hopkins, R. J.; Desyaterik, Y.; Kilcoyne, A. L. D.; Tyliszczak, T.; Fast, J.; Barnard, J.; Shutthanandan, V.; Cliff, S. S.; Perry, K. D.; Laskin, A.; Gilles, M. K. "Microscopic Characterization of Carbonaceous Aerosol Particle Aging in the Outflow from Mexico City," Atmos. Chem. Phys. 2010, 10, 961-976. Link Ditzler, L. R.; Karunatilaka, C.; Donuru, V. R.; Liu, H; Tivanski, A. V. "Electromechanical Properties of Self-Assembled Monolayers of Tetrathiafulvalene Derivatives Studied by Conducting Probe Atomic Force Microscopy," J. Phys. Chem. C 2010, 114, 4429. Link Galgano, J. J.; Karunatilaka, C.; Rethwisch, D. J.; Tivanski, A. V. "Atomic Force Microscopy Study of Photoreversible Nanoscale Surface Relief Grating Patterns on Side Chain Dendritic Polyester Thin Films," Colloids Surf. A 2010, 360, 167. Link Zaveri, R. A.; Berkowitz, C. M.; Brechtel, F. J.; Gilles, M. K.; Hubbe, J. M.; Jayne, J. T.; Kleinman, L. I.; Laskin, A.; Madronich, S.; Onasch, T. B.; Pekour, M. S.; Springston, S. R.; Thornton, J. A.; Tivanski, A. V.; Worsnop, D. R. "Nighttime Chemical Evolution of Aerosol and Trace Gases in a Power Plant Plume: Implications for Secondary Organic Nitrate and Organosulfate Aerosol Formation, NO3 Radical Chemistry, and N2O5 Heterogeneous Hydrolysis," J. Geophys. Res. 2010, 115, D12304. Link Runge, M. B.; Lipscomb, C. E.; Ditzler, L. R.; Mahanthappa, M. K.; Tivanski, A. V.; Bowden, N. B. "Investigation of the Assembly of Comb Block Copolymers in the Solid State," Macromolecules 2008, 41, 7687. Link Tivanski, A. V.; Li, J. K.; Walker, G. C. "Pressure-Induced Restructuring of a Monolayer Film Nanojunction Produces Threshold and Power Law Conduction," Langmuir 2008, 24, 2288. Link Hopkins, R. J.; Desyaterik, Y.; Tivanski, A. V.; Berkowitz, C. M.; Gilles, M. K.; Laskin, A. "Chemical Speciation of Sulfur in Marine Cloud Droplets and Particles: Analysis of Individual Particles from the Marine Boundary Layer over the California Current," J. Geophys. Res. 2008, 113, D04209. Link Moffet, R. C.; Desyaterik, Y.; Hopkins, R. J.; Tivanski, A. V.; Gilles, M. K.; Shutthanandan, V.; Molina, L. T.; Gonzales, R. A.; Johnson, K. S.; Mugica, V.; Molina, M. J.; Laskin, A.; Prather, K. A. "Characterization of Aerosols Containing Zn, Pb, and Cl from an Industrial Region of Mexico City," Environ. Sci. Technol. 2008, 42, 7091. Link Tivanski, A.V.; Hopkins, R.J.; Gilles, M.K. "Oxygenated Interface on Biomass Burn Tar Balls Determined by Single Particle Scanning Transmission X-ray Microscopy," J. Phys. Chem. A 2007, 111(25), 5448. Link Hopkins, R.J.; Tivanski, A.V.; Marten, B.D.; Gilles, M.K. "Chemical Bonding and Structure of Black Carbon Reference Materials and Individual Carbonaceous Atmospheric Aerosols," J. Aerosol Science 2007, 38(6), 573. Link Hopkins, R. J.; Lewis, K.; Desyaterik, Y.; Wang, Z.; Tivanski, A. V.; Arott, W. P.; Laskin, A.; Gilles, M. K. "Correlating Optical, Chemical and Physical Properties of Biomass Burn Aerosols," Geophys. Res. Lett. 2007, 34, L18806. Link Michelson, H.A.; Tivanski, A.V.; Gilles, M.K.; van Poppel, L.H.; Dansson, M.A.; Buseck, P.R. "Particle Formation from Pulsed Laser Irradiation of Soot Aggregates Studied with a Scanning Mobility Particle Sizer, a Transmission Electron Microscope, and a Scanning Transmission X-ray Microscope," Appl. Opt. 2007, 46, 959. Link Olynick, D.; Tivanski, A.V.; Gilles, M.K.; Tyliszczak, T.; Salmassi, F.; Liddle, A.; Liang, K.; Leone, S.R. "Scanning X-ray Microscopy Investigations into the Electron Beam Exposure Mechanism of Hydrogen Silsesquioxane Resists," J. Vac. Sci. Technol. B 2006, 24, 3048. Link Tivanski, A.V.; Walker, G.C. "Ferrocenylundecanethiol Self-Assembled Monolayer Charging Correlates with Negative Differential Resistance Measured by Conducting Probe Atomic Force Microscopy," J. Am. Chem. Soc., 2005 127, 7647. Link Tivanski, A.V.; He, Y.; Borguet, E.; Liu, H.; Walker, G.C.; Waldeck, D.H. "Conjugated Thiol Linker for Enhanced Electrical Conduction of Gold-Molecule Contacts," J. Phys. Chem. B, 2005, 109, 5398. Link Tivanski, A.V.; Walker, G. C. "The Role of Adhesion Forces in Nanoscale Measurements of the Conductive Properties of Organic Surfaces Using Conductive Probe AFM,". Proc. SPIE 2004, 5513, 14. Link Tivanski, A.V.; Bemis, J.E.; Akhremitchev, B.B.; Liu, H.; Walker, G.C. "Adhesion Forces in Conducting Probe Atomic Force Microscopy," Langmuir, 2003, 19, 1929. Link Tivanski, A.V.; Wang, C.; Walker, G.C. "Vibrational Mode Coupling to Ultrafast Electron Transfer in [(CN)5OsCNRu(NH3)5]- Studied by Femtosecond Infrared Spectroscopy," J. Phys. Chem. A 2003 107, 9051. Link